A quick attempt at an `AnteHandler` based approach to enforcing code size limits based on a param

antehandler.patch

diff --git a/x/wasm/alias.go b/x/wasm/alias.go
index 610ce97..3e32935 100644
--- a/x/wasm/alias.go
+++ b/x/wasm/alias.go
@@ -17,7 +17,6 @@ const (
 	TStoreKey                       = types.TStoreKey
 	QuerierRoute                    = types.QuerierRoute
 	RouterKey                       = types.RouterKey
-	MaxWasmSize                     = types.MaxWasmSize
 	MaxLabelSize                    = types.MaxLabelSize
 	WasmModuleEventType             = types.WasmModuleEventType
 	AttributeKeyContractAddr        = types.AttributeKeyContractAddr
diff --git a/x/wasm/keeper/ante.go b/x/wasm/keeper/ante.go
index 1ffd34b..b15cf87 100644
--- a/x/wasm/keeper/ante.go
+++ b/x/wasm/keeper/ante.go
@@ -4,6 +4,8 @@ import (
 	"encoding/binary"
 
 	sdk "github.com/cosmos/cosmos-sdk/types"
+	"github.com/cosmos/cosmos-sdk/types/errors"
+	paramtypes "github.com/cosmos/cosmos-sdk/x/params/types"
 
 	"github.com/CosmWasm/wasmd/x/wasm/types"
 )
@@ -94,3 +96,34 @@ func (d LimitSimulationGasDecorator) AnteHandle(ctx sdk.Context, tx sdk.Tx, simu
 	}
 	return next(ctx, tx, simulate)
 }
+
+// LimitMaxWasmCodeSizeDecorator ante decorator to limit the maximum size of
+type LimitMaxWasmCodeSizeDecorator struct {
+	paramSpace paramtypes.Subspace
+}
+
+func (l LimitMaxWasmCodeSizeDecorator) AnteHandle(ctx sdk.Context, tx sdk.Tx, simulate bool, next sdk.AnteHandler) (newCtx sdk.Context, err error) {
+	if !simulate {
+		return next(ctx, tx, simulate)
+	}
+
+	var maxWasmCodeSize uint64
+	l.paramSpace.Get(ctx, types.ParamStoreKeyMaxWasmCodeSize, &maxWasmCodeSize)
+
+	for _, msg := range tx.GetMsgs() {
+		switch msg := msg.(type) {
+		case *types.MsgStoreCode:
+			if uint64(len(msg.WASMByteCode)) > maxWasmCodeSize {
+				return ctx, errors.Wrapf(types.ErrLimit, "contract code cannot be longer than %d bytes", maxWasmCodeSize)
+			}
+		default:
+			continue
+		}
+	}
+
+	return next(ctx, tx, simulate)
+}
+
+func NewLimitMaxWasmCodeSizeDecorator(paramSpace paramtypes.Subspace) *LimitMaxWasmCodeSizeDecorator {
+	return &LimitMaxWasmCodeSizeDecorator{paramSpace: paramSpace}
+}
diff --git a/x/wasm/types/validation.go b/x/wasm/types/validation.go
index 374782c..380326a 100644
--- a/x/wasm/types/validation.go
+++ b/x/wasm/types/validation.go
@@ -5,8 +5,6 @@ import (
 )
 
 const (
-	MaxWasmSize = 500 * 1024
-
 	// MaxLabelSize is the longest label that can be used when Instantiating a contract
 	MaxLabelSize = 128
 )
@@ -15,9 +13,6 @@ func validateWasmCode(s []byte) error {
 	if len(s) == 0 {
 		return sdkerrors.Wrap(ErrEmpty, "is required")
 	}
-	if len(s) > MaxWasmSize {
-		return sdkerrors.Wrapf(ErrLimit, "cannot be longer than %d bytes", MaxWasmSize)
-	}
 	return nil
 }